[gae.py] Don't pass dispatch.yaml twice to 'gcloud app deploy'.
[gae.py] Don't pass dispatch.yaml twice to 'gcloud app deploy'.

R=ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org

Change-Id: I838f76063206bd751643f5da2caf89d146164e17
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/1522346
Reviewed-by: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>
Commit-Queue: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py